• Welcome to Overclockers Forums! Join us to reply in threads, receive reduced ads, and to customize your site experience!

OCing the CPU-NB?

Overclockers is supported by our readers. When you click a link to make a purchase, we may earn a commission. Learn More.

CrustyButt

Member
Joined
Oct 30, 2011
Location
123 West Awesome Ave. Blueberry, Pancakes
Okay guys, hows it going, to the point. I have my 955 (down below for V's and clock) OCed. My friend was telling me on steam about OCing the North Bridge and said it will in general give me a more "snappy" feature as soon as I boot up, so of curse I am pumped. So basically, I ahve no idea hpw to do this, and what normal voltages are for the NB, nor the "norm" clocks for AMD CPU's for the NB...I need help, I know my way around the BIOS, but I don't want to go messing with things that will be completely and utterly stable...thanks in advanced...load temps are down below, aswell, he told me (my friend) that it doesn't increase load temps, so hurray :D, or atleast not much :D
 
That CPU will probably do well with a CPUNB overclock to about 2600-2800 mhz and will need to be supported by a CPUNB voltage bump to about 1.25-1.3.
 
There i a markable performance increase with Phenom's by overclocking the CPU NB yes, as you can see in my sig i have boosted mine to 2850Mhz which is where the performance increase is about caped.

1.25v is a completely stable NB voltage for me but has moved my temps up a little from what you see in my sig, tho not much and it is still with in tolerances.

I have yet to 8 / 9 hour P-95 blend test with the NB OC but to be honest i don't think i will bother as a 1 hour test was fine and i don't see why a 9 hour test would be any different.
 
Does overclocking the CPU-NB allow for a higher overclock or tighter timings with RAM?
 
Does overclocking the CPU-NB allow for a higher overclock or tighter timings with RAM?

Not really ... higher CPU-NB clock = higher memory controller bandwidth and in some cases allows to make higher memory clock ( this mainly for FX cpus above 300MHz HT where you hit max memory multi - read for world records etc ;) )
Since memory speed on AMD is limited by IMC then overclocking CPU-NB is best way to improve memory performance.
 
At 3.9GHz my 960T will hit 55-56 core temps and so I assume that overclocking my CPU-NB will result in instability. However, going from 3.8GHz to 3.9GHz resulted in a noticeable increase in temps. Would I be better off going down to 3.8GHz and overclocking the CPU-NB?
 
Does overclocking the CPU-NB allow for a higher overclock or tighter timings with RAM?

erm? that's a good question and i don't actually know but i don't think its the case, AMD are limited only by the temps and how good you are at it, where overclocking AMD CPU's is concerned the sky is the limit and i have seen some clocked to ridiculous levels without overclocking the NB.

As for RAM timings, again i don't know, my timings Run in CL8 from 9 OC NB or not, and i can't get it to run CL7 no mater what i do as my RAM is junk.
 
Okay guys, so heres what I'm going toi do, I am going to test this in AMD Overdrive (this is what I did with my OCing, and then I changed it to that in the BIOS once I knew it was stable for ~2 hours) and then once I find it stable I'll change it in the BIOS, and limit on what "safe" voltages for the CPU-NB?
 
You generally don't want to go above 1.4V CPU-NB on air cooling.

On LN2, I've had chips survive 1.65 for sure, maybe 1.7 if I was angry. Even under air cooling just for temporary benchmarking, I have never gone above 1.45 on CPU-NB volts. CPU-NB at -190C will run at 4GHz+ typically on 1.55V.

In my experience, increased CPU-NB does improve benchmark performance in memory intensive tests. Like superpi32M where the memory performance is very important to your score.

Increased CPU-NB frequency will not help your CPU frequency, and it will not help your memory timings, however it will help the amount of bandwidth your memory can utilize - this is what gets you a slight performance improvement.

The only other benefit I am aware of with CPU-NB, and have tested thoroughly, is again under LN2 for extreme benchmarking. Sometimes when you hit max frequency - usually around 6.5 to 7GHz on Phenom II, giving the chip extra vcore does not help CPU frequency, but for some reason giving it extra CPU-NB will improve stability at higher CPU frequency. I don't know why, but I've tested it numerous times to be true.

In regular usage, increased CPU-NB has never shown me an observable difference.
 
With some AMD CPUs like the Thuban core series there is the feeling out there that increasing the HT Link and CPUNB frequency helps with stability and in my experience a small bump in the CPUNB voltage to about 1.25 helps with stability on most overclocked AMDs even when the CPUNB itself isn't overclocked.
 
I've heard that as well.

While that is something we've heard though, I'm not sure I believe the HTlink opinions that are out there. When I've been at 7 or 8 Ghz on phenom and bulldozer, I've always kept HTLink right at about 2GHz. If it doesn't make a difference for extreme frequencies like that, my thought is that it doesn't make a difference at regular frequencies either.

For an example related to this, while running Superpi32m at 7.7GHz on an FX-8120, increasing CPU-NB frequency but changing nothing else could take 5-10 seconds off my total superpi32m time (about 11 minutes to finish). Changing HTLink had no effect on my time, at frequencies between 1600MHz and 2400MHz - there was no difference.

I know you aren't going after crazy frequencies, and maybe my results don't seem relevant as they are just benchmarking runs. However, I think they lend some insight into how the CPU, CPU-NB, and HTlink frequencies play together. I don't know a whole lot technical about this stuff - I just get it cold and run different settings to see what works best for me, so I'm just sharing my experience. I wouldn't put more stock in my input than I would anyone elses though. Especially when it comes to daily settings and regular overclocks, a lot of people around here know a lot more than me.
 
All my attempts to overclock the CPU-NB were met with failure. It would appear that my 960T is just happier at stock CPU-NB volts/frequency. :shrug:
 
You generally don't want to go above 1.4V CPU-NB on air cooling.

On LN2, I've had chips survive 1.65 for sure, maybe 1.7 if I was angry. Even under air cooling just for temporary benchmarking, I have never gone above 1.45 on CPU-NB volts. CPU-NB at -190C will run at 4GHz+ typically on 1.55V.

I was running FX8120 with CPU-NB up to 1.88-1.9V on SS :D .. at about 1.9V cpu is shutting down :p From ~1.7 to 1.9V there is no difference in any clocks ( or I need better cooling ). No matter if I set 1.55 or more I get the same max CPU-NB clock that is no more than ~3080MHz. I wasn't able to set anything stable above ~2800MHz ( FX cpu ).
( if anyone is curious then there is no visible degradation of my FX8120 while it was running at so high voltages - just don't try it at home ;) )
Phenoms II can run at much higher CPU-NB and I was able to set quite stable 3000MHz CPU-NB with 300MHz FSB on box cooler ;)

@wnnbgwrrr try 1 step higher than stock CPU-NB and set clock 1:1 with HT. You can add ~0.10V to CPU-NB.
 
Back